Field of the Invention
The formation of sulfonate containing polymers has been clearly defined in a number of U.S. Pat. Nos. 3,642,728; 3,836,511; 3,847,854; 3,870,841; and 3,877,530. These patents teach the formation of sulfonate polymers by contacting a polymer having olefinic unsaturation with a sulfonating agent.
This application differs from the previously identified U.S. patents in that the instant process is directed at the free radical emulsion polymerization of a polymerizable vinyl monomer and a sulfonate containing monomer to form a substantially gel-free terpolymer having a major portion of the conjugated diene and a minor portion of the sulfonate containing monomer, whereby the terpolymer is water insoluble and substantially water insensitive. The sulfonate containing monomer is characterized by the formula: ##STR1## wherein Y is a cation selected from the Groups I-A, II-A, I-B or II-B of the Periodic Table or an amine of the formula NHR.sub.1 R.sub.2 where R.sub.1 and R.sub.2 can be aliphatic groups of C.sub.1 to C.sub.12.
The formed terpolymers contain about 13 to about 48 wt. % styrene, more preferably about 20 to about 40 wt. % and most preferably about 25 to about 35 wt. %; about 55 to about 88 wt. % of butadiene, more preferably about 55 to about 80 wt. %, and most preferably about 65 to about 75 wt. %. The amount of sulfonate comonomer to be introduced into these systems can be defined in terms of weight percent chemically combined sulfur. The preferred range is at least 18 to 100 meq. of sulfonate groups per 100 grams of polymer.